Pediatric Primary Care (99 page)

3.  Side effects of medication.

4.  If after several weeks of therapy symptoms continue, may need increased dose of antithyroid medication.

II. HYPOTHYROIDISM

A.  Condition resulting from deficient production of thyroid hormone or defect in hormonal receptor activity.

B.  Etiology.

1.  Hypothyroidism may be congenital or acquired.

a.  Congenital hypothyroidism.

• Most commonly from inadequate production of thyroid hormone due to agenesis, dysplasia, ectopy of thyroid, or autosomal recessive defects in thyroid hormone synthesis and defects in other enzymatic steps in T4 synthesis and release.

• Most common preventable cause of mental retardation.

b.  Acquired hypothyroidism most commonly caused by autoimmune destruction (Hashimoto thyroiditis).

C.  Occurrence.

1.  One case per 3500 persons for congenital hypothyroidism.

2.  Acquired hypothyroidism: 6% of age 12-19-year olds have evidence of autoimmune disease.

a.  Depending on diagnostic criteria, may be as high as 10% in young females. Higher incidence in females (2:1).

b.  Congenital if untreated condition results in profound growth failure, developmental cognitive delay (cretinism).

c.  When untreated in older children: growth failure, slow metabolism, impaired memory.

D.  Clinical manifestations.

1.  Congenital.

a.  Constipation.

b.  Hypotonia.

c.  Hypoglycemia.

d.  Hypothermia.

e.  Poor feeding.

f.  Hoarse cry, noisy respirations.

g.  Large for gestation.

2.  Acquired.

a.  Asymptomatic goiter.

b.  Hoarseness, dysphagia.

c.  Mild weight gain.

d.  Slow growth/delayed osseous maturation.

e.  Lethargy, sleep disturbance/sleep apnea.

f.  Cold intolerance.

g.  Constipation.

h.  Sexual pseudoprecocity.

i.  Headaches.

j.  Depression.

E.  Physical findings.

1.  Congenital.

a.  Large for gestation infant.

b.  Hypotonia, puffy face.

c.  Wide anterior, posterior fontanel.

d.  Prolonged jaundice.

e.  Abdominal distention.

f.  Feeding difficulties/slowed gastric motility.

2.  Acquired.

a.  Visual problems.

b.  Precocious puberty (young children).

c.  Dry skin.

d.  Slowed pulse.

e.  Delayed puberty.

f.  Coarse, sparse hair.

g.  Delayed dentition.

h.  Ankle and feet swelling.

i.  Short stature.

F.  Diagnostic tests.

1.  Newborn screen for T4: if low, then TSH drawn for definitive testing.

2.  Serum thyrotropin concentration/TSH.

3.  T4 and T3.

4.  Serum antithyroid globulin antibodies.

5.  Antithyroid peroxidase.

6.  Radionucleotide studies.

7.  Radioisotope-based thyroid scanning.

G.  Differential diagnosis.

1.  Endemic goiter/nutritional iodine deficiency.

2.  Chromosomal abnormalities such as Turner syndrome.

3.  Precocious puberty in young child.

4.  Familial short stature.

5.  Constitutional growth delay.

6.  Growth hormone deficiency.

7.  Chronic bowel syndrome.

8.  Renal disease.

9.  Malnutrition/gluten-induced enteropathy.

10.  Cortisol excess.

11.  Diabetes mellitus.

H.  Treatment.

1.  Levothyroxine (Levothroid, Levoxyl, Synthroid), a synthetic drug identical to human T4, is preferred thyroid hormone replacement.

2.  Neonates: initial doses 10-15 mcg/kg PO every morning before meals. Dosage titrated on basis of thyroid function tests every 3 months until 2 years of age. Desired T4 range: 10-15 mcg/dL.

3.  Children: 2-6 years of age: 5 mcg/kg PO every morning before meals; 6-12 years of age: 4-5 mcg/kg PO every morning before meals.

4.  Adolescents: 100-150 mcg PO every morning before meals.

5.  With age, levothyroxine dose decreases on weight basis.

I.  Follow up.

1.  Monitor for behavior change, school performance.

2.  Monitor serum TSH 2-3 months after change in dosage.

3.  Monitor for symptoms of hypothyroidism, hyperthyroidism.

J.  Complications.

1.  Noncompliance with treatment protocol.

K.  Education.

1.  Educate parents on signs/symptoms of hypothyroidism and hyperthyroidism.

2.  Allow child to take responsibility for own care as soon as old enough (9-10 years of age).

III. SHORT STATURE

A.  Generally accepted definition is stature below third percentile, or two standard deviations (SD) below mean, for age.

B.  Etiology.

1.  Familial short stature.

2.  Constitutional growth delay.

3.  Growth hormone deficiency.

4.  Chromosomal disorder/Turner syndrome.

C.  Occurrence.

1.  Growth hormone deficiency estimated 10,000 to 15,000 children in United States.

2.  Turner syndrome: 1 in 2500 female births.